<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .wrap{
      width: 500px;height: 400px;
      border: 1px solid red;
    }
    .content{
      position: absolute;
      top: 0;left: 0;
      width: 300px;height: 200px;
      border: 1px solid blueviolet;
    }
    .item{
      position: absolute;bottom: 0;right: 0;
      width: 100px;
      height: 100px;border: 1px solid yellowgreen;
      z-index: 11;
    }
  </style>
</head>
<body>
  
  <div class="wrap">
    <div class="content">
      <div class="item"></div>
    </div>
  </div>
</body>
</html>